Decimeter waves with a length of stacked in a gap of 10 cm - 1 m. The feature is the basis for naming devices. At a frequency, electromagnetic oscillations propagate predominantly in a straight line, avoiding to bend around the earth's surface, partially reflected by the troposphere. Therefore, long-distance communication UHF is difficult, the range does not exceed 100 km. Can a hand-held decimeter antenna be assembled? Maybe actively going to amateur engineers.
Beer banks will receive television broadcasting
The frequencies of UHF are located in the 300 MHz - 3 GHz segment. There are many commercial, publicly accessible channels.
Transmission “Cheap and Angry” taught to catch the First Channel Muscovites. According to reports, transmitted by the MW band, the sound is adjacent to FM radio stations, a homemade design, demonstrated by the presenter, is used by the UHF.
You will need two beer cans with a capacity of 0.5 liters( more volume, lower frequencies than accepted).You can save by buying mineral water, juice in cans. For fastening of the mentioned containers you will need a frame.
The first channel recommends the use of a wooden board 10 cm wide, enthusiasts have come up with a constructive solution. Banks are invited to hang on an ordinary wooden hanger. A room-mounted decimeter antenna, made in this way, is easily placed on the window handle, wall nail.
In addition to two beer cans, you will need:
- A pair of sharp screwdrivers( screws) with a diameter of 2-3 mm, a screwdriver.
- A piece of coaxial cable from the antenna to the TV.
- One connector of a standard socket.
- Scotch tape, insulating tape.
- Useful soldering iron, rosin, solder, a pair of terminals for the above p. 1 screws.
Begin with the seal of the connector, the terminals in the wire. The first will be located on the TV side, the second - from the opposite end( lived, screen).Both terminals need to be diluted by 12 cm.
The antenna design avoids difficulties: the banks are fixed with a horizontal crossbar with the nets facing up to 75 mm from each other. Begin assembly by attaching the terminals to the necks with screws. Twist to failure there is no need, the wires should tightly press against the banks.
In parallel to each other, containers are fixed with tape on a hanger. Homemade decimeter antenna is ready. Hanging a hanger in the place of the best reception - first you need to find one, - cover with a curtain, clothes. According to eyewitnesses, the design works, equipped with banks of a more modest displacement. You can actively experiment by changing the distance between capacities, assessing the visual quality of the image.
Ring of standard television wire
The design does not require anything besides coaxial cable with resistance of 75 Ohm( RK 75).A flat ring is curved out of the 530 mm long section, reinforced with plywood and plexiglass. High input resistance will not allow you to create a direct connection to the TV, using a special matching device - U-knee.
A piece of cable with a length of 175 mm is bent in the shape of a letter U. The ends are aligned with the edge of the wire going to the TV on both sides. The design is fastened with adhesive tape, any other suitable material. Three screens are soldered to each other. The veins of the U-knee are connected to the screen of the curved ring on both sides, the central wire of the television cable is from one side.
A passive UHF antenna is being obtained. For outdoor use, cover the cable with compound, resin, enclose the product with a strong, impermeable plastic casing.
Wi-Fi Rings, Televisions
Two aluminum contours
“Cheburashka” firmly caught nothingness, it turned out - not definitively. Many have seen a flat aluminum plate, equipped with huge rings on the sides, how to make a decimeter antenna with your own hands? You need two flat aluminum rings with an outer diameter of 100 mm and an inner diameter of 38 mm. Each is cut through a 5 mm wide slit.
It turns out that two circuits will avoid the use of a transformer. The framework will be a glass-fiber laminate plank, a piece of solid wood. Both rings are mounted with a distance between the centers of 103 mm towards the slots. The upper, lower edges of the slots are pairwise connected. The screen, the core of the coaxial cable going to the TV, are connected to the resulting pairs.
Antenna decorates the balcony, room, roof. Shorter than the length of the coaxial cable to the TV, more confident reception.
Circuit formed by circular vibrators. When a wave is horizontally polarized, a phase difference between the symmetric rings located one above the other does not occur, the cable removes the received radiation from the isthmus.
The resonant frequency of the product is 802 MHz, allowing you to use Wi-Fi 900 MHz networks, watching television channels 38 - 64. The antenna of the UHF range fits perfectly with the coaxial cable RC-75, shows a gain of 15 dB.
The structure is positioned vertically, the slots must be one above the other, respectively, the polarization of the received signal is horizontal.
Two contours of the getinax
Amateur may seem to be an attractive other method of manufacturing the described design: on the board of the getinax, textolite with one-sided foiling, the required figures are cut. Between the rings according to the scheme described, it is necessary to leave a contact bridge with an external width of 20 mm, with a 5-mm slot inside. Under the coaxial cable, two mirror holes are drilled.
The method is convenient: four fastening slots cut in the getinax by the edge of the sheet will allow you to firmly fasten the product. Use:
- wall;
- frame;
- roof.
The design is easily transposed to high, low frequencies by changing the geometric dimensions of the circles. Optimum input impedance is easier to choose empirically( by trying practical dimensions).
Sealing is made of plexiglass plates, with dimensions equal to getinkax. The perimeter of the gap is sealed with liquid nails.
A curious feature of the type of antennas is the possibility of creating a phased array. Two identical structures are mounted vertically on top of each other, separated by a verified distance( the described example is 406 mm between the centers of the eights).To create a single lattice, a summing device is used, which is formed by two outlets with a length of 325 mm, held together in the middle. Coaxial cable is soldered to the junction.
One Circuit with a Transformer
Now that it is clear how to make a decimeter antenna, consider the above-mentioned transformer, which is electrically isolated from the antenna and TV.The basis is the construction described above. The circuit is one, both ends are closed on the primary winding of the miniature transformer, the coaxial cable of the TV is soldered to the secondary.
The core formed by several turns of wire plays the role of a matching device. For the manufacture of the hinged element, you must take the ring core with an outer diameter of less than 10 mm, a thickness of 2-3 mmA wire with a diameter of 0.2 - 0.25 mm winds two windings side by side, the number of which is several turns each.
The design is not inferior to the efficiency of the dual-circuit models described above. Polarization is horizontal( the slot should be vertical).
Digital TV
Decimeter antennas for digital television are made relatively simply. You will need a wooden square with a diagonal of 200 mm, or a similar object made of Plexiglas, a fair amount of the usual RK-75 cable.
The variant under consideration is part of a zigzag antenna, which perfectly serves the reception range of digital channels, regardless of whether there is direct line of sight to the tower. To improve performance should get an amplifier.
The tip of the wire is trimmed to 20 mm. Then a 175 mm square is bent out of the cable. The end is bent outward by 45 degrees, the beginning is bent down with the stripping of a section of 20 mm, tightly attached to the end. Provides reliable contact screens. The end of the vein hangs in the air.
At the corner opposite to the beginning, the protective layer is cut off, the screen in the 20 mm section will be the top of the antenna. The cable square is symmetrically fastened around the perimeter of the wooden sheet. In the area of the closure of the screens - where the beginning and the end are attached to each other - copper brackets made of thick wire are used for fixing to improve electrical contact.
This is how you make a UHF antenna with your own hands. For outdoor use, it must be protected by a plastic case against the effects of the external environment, or securely hidden by a hole in the attic window. Through metal, tile, slate signal passes rarely. If the roof is made of PVC, plastic, fabric, similar materials, it is permissible to place the product in the attic.
To block the effect of multipath, a reflector in the shape of a piece of wood is used. Fastened with ebony racks coaxially antenna.
The considered designs are intended to conduct reception of waves with linear polarization. You may need to use a spiral antenna.
